A New Family Tree For One Of The World's Most Endangered Mammals

With 106 living species and almost every single one of them endangered, Madagascar’s trademark mammal, the lemur, is in dire need of conservation. But how can studying their past inform scientists about their future? New research out today in Systematic Biology by James Herrera of the American Museum of Natural History and Professor Liliana Dávalos of the Stony Brook University reveals how the most complete lemur family tree ever constructed can begin to help these iconic creatures.

Lemurs are primates endemic to the island of Madagascar. Judging by size, appearance, and ecology, they are quite a diverse group despite being limited to one, albeit large, island. They range in size from the mouse lemur, weighing in at 30 grams, to the Indri lemur topping out at 22 pounds—but once they were nearly the size of gorillas. An extinct lemur known as Archaeoindris weighed over 300 pounds and was alive just around 2000 years ago when humans first reached Madagascar. Herrera and Dávalos used new methods to combine both DNA and morphological evidence of fossil and living lemurs and other related primates to assemble the most complete evolutionary tree possible, which leads to some interesting new conclusions about the history of this enigmatic group.

They find that all of the large bodied lemurs start to disappear 2000 years ago, potentially indicating body size and hunting put them at risk for extinction. James Herrera explains: “The current evidence points to hunting and widespread use of fire to clear forests as the ultimate causes of the demise of these giant lemurs. There is evidence forests were shrinking naturally because of a long dry period at about the same time, but many bones have marks of butchery, pointing to human influence.”

A new time-calibrated family tree of lemurs shows when they diversified and when they went extinct. (Image credit: Herrera and Dávalos 2016, provided by SUNY Stony Brook)

They also confirmed that lemurs evolved between 50-60 million years ago, some 30 million years after Madagascar split from Africa and India-- but early lemur fossils are still found in Africa. Then how did the lemurs make their way to Madagascar? Professor Dávalos describes how they potentially could have floated on vegetation rafts for 300 mile across the ocean: “As hard to believe as that may be, there are several reasons to believe it was possible. First, the currents at that time flowed from Africa to Madagascar, suggesting favorable conditions for such a dispersal event. Second, during cool and dry periods in the history of the earth, the sea level would have been lower exposing more land area and possibly stepping-stone islands along the way.”

This sort of research is vital because the evolutionary and geographic history of lemurs is a complicated one. As Herrera fittingly summarizes: “With all living and extinct lemurs together in the same tree, we can begin to understand how evolution and extinction have worked in the past, and project risks to these primate species into the future.”

Shaena Montanari is a paleontologist and science communicator. Follow her on Twitter at @DrShaena for the latest natural history and fossil news.